LEDs have attracted much attention as backlights for liquid crystal display devices due to a long service life and low power consumption. In recent years, LEDs have been used not only in liquid crystal display devices for portable phones but also in liquid crystal display devices of TVs. One consideration when LEDs are used for backlighting, though, is uniformity of light emission intensity across the display. In order to obtain general uniformity of the light emission intensity, LEDs are arranged on a substrate, and a light emission control circuit is coupled to each LED to control the brightness and the light emission time of the LED. However, compactness can be an issue due to the large number of wires that are generally employed
In conventional devices, LED controllers, each of which has integrated light emission control circuits, are coupled in series. The light emission data indicating the light emission condition of each LED is transmitted serially in synchronization with a clock signal from light emission control circuits in the previous stage to those in the next stage. An external latch signal is input to each light emission control circuit to simultaneously change the light emission status of each LED. Accordingly, light emission data can be input by one wire to several LED controllers coupled in series, and the light emission conditions of LEDs coupled to the respective LED controllers can be set by one wire. However, when the light emission data for LEDs is transmitted serially in this manner, a long time delay is present when transmitting the light emission data during light-on inspection for each LED, and it is difficult to freely turn on/off the LEDs.